Arbitrary File Write via Archive Extraction (Zip Slip) Affecting github.com/bblfsh/bblfshd/runtime Open this link in a new tab package, versions *


0.0
medium
  • Exploit Maturity

    Proof of concept

  • Attack Complexity

    High

  • User Interaction

    Required

  • Scope

    Changed

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  • snyk-id

    SNYK-GOLANG-GITHUBCOMBBLFSHBBLFSHDRUNTIME-1566478

  • published

    17 Aug 2021

  • disclosed

    17 Aug 2021

  • credit

    Chris Smowton

How to fix?

A fix was pushed into the master branch but not yet published.

Overview

github.com/bblfsh/bblfshd/runtime is a provides the runtime environment to execute the bblfsh drivers.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). The unsafe handling of symbolic links in an unpacking routine may enable attackers to read and/or write to arbitrary locations outside the designated target folder.

Details

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:


+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys